While I'd rather have an RB-anything powered car, I must be one of the few people on IA that ~likes~ SR swaps. Of course, it sounds sorta dumb to say it, but I liked SR swaps long before SR swaps were cool. I first saw a Silvia grey-marketed into the US by a friend of my dad's when we lived in Memphis on the Naval Air Station there. Fell in love with the way the S-13 Silvia looked and sounded, wanted one ever since. I'd rather have a real-deal, but I'll be honest, an SR-swapped 240 would be fine for me with a front end swap to match on a coupe.


To the point of the thread, and to answer a bit about the RB vs SR, 6>4 for fluid dynamics reasons. The RB20 also has a shorter stroke than the SR, but is not 86mm bore, which makes it smaller overall piston size than the SR. The best RB to SR comparison would be an "RB24" (See more below), which is 86 bore like the other RBs, and 70 stroke, just like the RB20. Add the extra cylinders, and of course the extra valves that go with it, and you have significantly increased flow. The RB20DET stock spat 210bhp at 6400, the SR20DET from the S15 was 245bhp at 6400. YMMV, but the S15's engine also came out about 6-7 years after the RB20 stopped getting put into engines. The RB20's contemporary SR20 produced about the same amount of brake horses.


RB24 isn't a manufactured RB engine, it's an RB25 block with an RB20 crank, essentially de-stroking and de-compressing the engine. There were a few made for Cefiro taxis that were exported to China, but you can replicate the same kind of engine. The de-stroked engine can rev higher with the right valvetrain, and would have a lower compression ratio for absurd boostage. RBs besides the 20 were much closer to square, and the SR engine is perfectly square at 86x86. The point is, it depends on how much boost you run through the engine, but an RB20 will typically produce less power but more torque thanks to the extra cylinders and flow. There's also just something to be said about Straight-6s. I'm a I-6 fanboy for life.

Edit: Oh, and the reason why I brought up the RB24 at all is because you could really impress people by pointing out you have a 6 cylinder 2.4l 240sx. It just wouldn't be worth the work of buying the parts and building it. I think the production one for the Cefs used a higher flowing head too, don't remember much about it.